THE STUDY OF CURVES OF THE TRANSIENT CURRENT IN POLYTETRAFLUOROETHYLENE BY MEANS OF FOURIER ANALYSIS

Experimental transition current curves for polytetrafluoroethylene after exposure to high-energy ionizing radiation are obtained. The transient current curves in irradiated polytetrafluoroethylene are analyzed based on the discrete Fourier transform. It is shown that there is an intense maximum of dielectric absorption in the infralow frequency region. This maximum is characterized by abnormally large values of the dielectric increment, permittivity, and the dielectric loss factor. It is concluded that the volume polarization of the irradiated polytetrafluoroethylene is uniform. The polarization observed in this frequency range is associated with the activation of migration of trapped charge carriers within microscopic regions.

The Effect of the Coating Layer and the Doped Ion Concentration on the Dielectric Properties of SiO2-PANI Electrorheological Fluid

The silicon dioxide particles are coated by polyaniline (PANI) under low temperature, and the doped ion concentration in PANI was adjusted by ammonia with different pH. The dielectric properties of PANI/SiO2 eletrorheological (ER) fluids are measured by impedance analyzer. The results indicated that the dielectric increment and relaxation frequency of ER fluid were enhanced after surface modification of SiO2, which are positive to the ER effect. Moreover, the pH of ammonia can change the relaxation frequency of ER fluid, which can improve the response ability of ER fluid to electric field.

Nonlinear Dielectric Relaxation in Solutions of 6CHBT in Nonpolar Medium

The frequency dependence of the nonlinear dielectric increment was studied for benzene solutions of the nematogenic molecule 4-(trans-4'-n-hexylcyclohexyl)isothiocyanatobenzene (C6H13CyHx-Ph-N = C = S, 6CHBT) at 25°C. The increment was induced by a quasi-static electric field of high strength (107 V/m), and its relaxation was detected by an alternating field of low strength (102 V/m) in the fre-quency range 1 MHz-3 GHz. The results are discussed in the framework of Coffey's theory.